Utilization of Olive Mill Waste in Microbial Electrolysis Cell

Olive oil production is a source of huge amount of residuals knowns as OMW (Olive Mill Waste). The sustainable management and treatment of this waste is challenging due to presence of high amount of specific pollutants. The OMW is characterized by very high COD to BOD ratio with considerable content of polyphenols reaching up to 15g/l. Due to this, the biological utilization of OMW could be hindered or very slow when the conventional aerobic and anaerobic methods are used.In this study, the Microbial Electrolysis Cell (MEC) technology was applied as an alternative treatment approach. The method offers COD reduction and energy recovering in the form of hydrogen. The results demonstrated up to 65% efficiency in terms of COD and polyphenols removal which suggest that MEC, could be considered as an initial treatment stage in OMW utilization

Membrane filtration pretreatment preceding struvite precipitation

The ability of Microfiltration (MF) and Ultrafiltration (UF) technique for separation of organic matter in treatment of nutrient rich fluids is investigated in the study. Such separation is of great importance in case of performing magnesium-ammonium phosphate hexahydrate (struvite) precipitation as the struvite yield depends negatively on organic matter content.The advantage of cross-flow UF in separating the particulate organic matter and soluble phosphorus (P) was proved. Such a process allows COD removal rates over 99 %, while the P in permeate was kept high enough to perform a successful P precipitation as struvite

Phosphorus consumption. From linear to circular flow

Wastewater and waste sludge are generated in all parts of the world during domestic and industrial activities. Conventional wastewater treatment methods generate a highly concentrated municipal sludge, which needs to be disposed of effectively without leading to secondary pollution. Animal manure and post generated manure wastewater are another environmental concern. Both of the above wastewater and sludge/manure are rich in organic/inorganic forms of carbon, nitrogen (N) and phosphorus (P). Anthropogenic and industrial activities in the global biogeochemical cycles have resulted in a drastic one-way mobilization of these resources into the atmosphere and the environment.The current intensive agriculture requires huge quantities of nitrogen (N) and Phosphorus (P) containing fertilizers. The industrial production of ammonia and nitrates is quite energy demanding; however, nitrogen is abundantly present in the nature and therefore it is a non-restricted resource for nitrogen derivate production. Unlike nitrogen, P can be obtained primarily from mineral deposits available only in few geographic locations. The phosphate rock reserves are finite and the current intensive fertilizer production based on economically mined rocks could last only another 50-100 years. Since phosphates are available only in limited geographic locations and the recognition that geologic phosphates are a non-renewable resource, Phosphorus recovery becomes a crucial for sustainable food production as EU depends for 90% on import of phosphate rocks (European Commission 2017). Within the EU only Finland has some phosphate rocks. The list of supplying countries is quite short; more than 70% of the present known global reserves of phosphate rock are located in Morocco as of all mined and processed phosphate rock (2009).  Phosphorus, being a finite resource with deficits starting approximately from the year 2070 due to increased demand might also result in high prices and reliance on single point sources, giving them monopoly over the market.The EU phosphorus flows show that the main losses of phosphorus in the food sector are through sewage sludge, other waste water and food waste. In general, phosphorus can be recycled, mainly from wastewater (e.g. sewage water), manure and organic waste (e.g. wasted food). Thus, wastewater can be considered as a renewable source of N and P. Instead of releasing the N and P rich wastewater into coastal and inland waters increasing eutrophication risk their utilization can be beneficial resulting in multiple benefits like nutrient recovery, water reclamation for reuse and maintenance of ecological balance in aquatic systems.Presently, the recovery and reuse of P is still far from being a main stream practice. Yet, the techniques already accepted and applied differ by the origin of the used matter (wastewater, sludge, ash) are mainly focused on the process of precipitation. One of these techniques is struvite precipitation, which can be implemented in wastewater treatment plants that use enhanced biological or semi biological/chemical phosphorus removal. Struvite (magnesium ammonium phosphate or MAP (MgNH4PO4·6H2O)) is formed by a basic precipitation reaction in different stages of the wastewater treatment process where magnesium (Mg2+), ammonium (NH4+) and orthophosphate (PO4−3).The article discusses the progress in extracting P from sewage sludge and animal manure, the conditions to create optimal conditions for struvite precipitation in such media and the way to overcome the problems associated with choosing the right Mg source, pH adjustment and the non-acceptable level of organic matter in the initial suspension